1. Field of the Invention
The present invention relates to a light projection structure in which a reflective member reflects light emitted from a light emitting member disposed at a focal point and projects the light, and to a lighting apparatus including the light projection structure.
2. Description of Related Art
A light projection structure including a reflective member (reflection mirror) and a light emitting member is well known. The reflective member has a reflective surface, which is formed as a concave surface such as a paraboloid. The light emitting member is disposed at a focal point of the reflective member and contains a fluorescent material. The fluorescent material is excited so that light is emitted from the light emitting member. The reflective member reflects the light. The light projection structure projects substantially parallel rays.
In a conventional example, the reflective member has a shallow reflective surface, in which its focal point is positioned at an exit of the reflective member, and the light emitting member is disposed at the focal point (e.g., U.S. Pat. No. 7,165,871).
In another conventional example, the reflective member has a reflective surface having an intermediate depth, in which its focal point is positioned inside the reflective member, and the light emitting member is disposed at the focal point (e.g., Japanese Patent Application Laid-open No. 2004-354495).
Even if the depth of the reflective surface is different, parallel rays can be projected from the light projection structure as long as the light emitting member is a complete point light source and is disposed at the focal point. However, the light emitting member has a certain size. It is impossible to realize an optically ideal, complete point light source.
Conventionally, there has been no discussion about optical efficiency of the reflective member with respect to a light source which is not optically complete point light source but has a certain size, in terms of relationship with a depth of the reflective surface and a position of the light emitting member.